U.S. patent number 8,432,818 [Application Number 11/966,074] was granted by the patent office on 2013-04-30 for system and method for link adaptation overhead reduction.
This patent grant is currently assigned to Research In Motion Limited. The grantee listed for this patent is Zhijun Cai, Takashi Suzuki, James Earl Womack, Gordon Young. Invention is credited to Zhijun Cai, Takashi Suzuki, James Earl Womack, Gordon Young.
United States Patent |
8,432,818 |
Cai , et al. |
April 30, 2013 |
System and method for link adaptation overhead reduction
Abstract
Systems and methods of providing link adaptation information
feedback are provided. A mobile device that receives packets
generates link adaptation information based on incorrectly received
packets. This can involve sending link adaptation information in
association with NACKs (negative acknowledgements) generated by the
mobile device. The network receives this link adaptation
information and performs link adaptation accordingly.
Inventors: |
Cai; Zhijun (Euless, TX),
Womack; James Earl (Bedford, TX), Young; Gordon
(Shipston-on-Stour, GB), Suzuki; Takashi (Ichikawa,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Cai; Zhijun
Womack; James Earl
Young; Gordon
Suzuki; Takashi |
Euless
Bedford
Shipston-on-Stour
Ichikawa |
TX
TX
N/A
N/A |
US
US
GB
JP |
|
|
Assignee: |
Research In Motion Limited
(Waterloo, Ontario, CA)
|
Family
ID: |
40129164 |
Appl.
No.: |
11/966,074 |
Filed: |
December 28, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080310400 A1 |
Dec 18, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60944367 |
Jun 15, 2007 |
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Current U.S.
Class: |
370/252; 370/352;
370/465 |
Current CPC
Class: |
H04L
1/0027 (20130101); H04L 1/0029 (20130101); H04L
1/1671 (20130101); H04W 28/18 (20130101); H04W
28/0289 (20130101); H04L 65/80 (20130101); H04L
1/0034 (20130101) |
Current International
Class: |
G01R
31/08 (20060101); H04J 3/14 (20060101); H04L
1/00 (20060101); H04L 12/26 (20060101); G06F
11/00 (20060101); G08C 15/00 (20060101); H04J
1/16 (20060101) |
References Cited
[Referenced By]
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Primary Examiner: Nawaz; Asad
Assistant Examiner: Mullen; Justin N
Attorney, Agent or Firm: Conley Rose, P.C. Brown, Jr.; J.
Robert
Parent Case Text
RELATED APPLICATION
This application claims the benefit of U.S. Provisional Patent
Application No. 60/944,367 filed Jun. 15, 2007.
Claims
We claim:
1. A method in a mobile device comprising: receiving packets;
transmitting fast MCS (modulation and coding scheme) link
adaptation information based on incorrectly received packets,
wherein transmitting fast MCS link adaptation information based on
incorrectly received packets comprises: transmitting NACKs
(negative acknowledgements) that indicate which packets were
received incorrectly; and transmitting fast MCS link adaptation
information in association with the NACKs when the NACKs
transmitted by the mobile device satisfy at least one other
criteria, wherein transmitting fast MCS link adaptation information
when the NACKs transmitted by the mobile device satisfy at least
one other criteria comprises: transmitting fast MCS link adaptation
information when the transmitted NACKs include a number of
transmitted NACKs within a sliding window that is greater than a
predefined number.
2. The method of claim 1, wherein receiving packets comprises
receiving packets that are VoIP (voice over internet protocol)
packets, constant rate packets, real-time packets or constant rate
real-time packets.
3. The method of claim 1, wherein the fast MCS link adaptation
comprises at least one of: a CQI (channel quality indication); a
received signal value; and an MCS decision made by the mobile
device.
4. The method of claim 1, further comprising: combining the fast
MCS link adaptation information with NACKs using code division
multiplexing.
5. The method of claim 1, further comprising: transmitting slow MCS
link adaptation information from less frequently than transmitting
fast MCS link adaption information.
6. A method in a wireless network comprising: transmitting packets;
receiving fast MCS (modulation and coding scheme) link adaptation
information based on transmitted packets that were incorrectly
received; based on the fast MCS link adaptation information,
adjusting an MCS used to transmit the packets, wherein receiving
fast MCS link adaptation information based on transmitted packets
that were incorrectly received comprises: receiving NACKs (negative
acknowledgements) that indicate which packets were received
incorrectly; and receiving fast MCS link adaptation information in
association with the NACKs when the NACKs satisfy at least one
other criteria; wherein receiving fast MCS link adaptation
information when the NACKs received from a mobile device satisfy at
least one other criteria comprises: receiving fast MCS link
adaptation information when the received NACKs include a number of
received NACKs within a sliding window that is greater than a
predefined number.
7. The method of claim 6, wherein transmitting packets comprises
transmitting packets that are VoIP (voice over internet protocol)
packets, constant rate packets, real-time packets or constant rate
real-time packets.
8. The method of claim 6, wherein the fast MCS link adaptation
comprises at least one of: a CQI (channel quality indication); a
received signal value; and an MCS decision made by the mobile
device.
9. The method of claim 6, further comprising: combining the fast
MCS link adaptation information with NACKs using code division
multiplexing.
10. The method of claim 6, further comprising: receiving slow MCS
link adaptation information less frequently than receiving fast MCS
link adaption information; and making MCS decisions based on the
slow MCS link adaptation.
11. The method of claim 6, further comprising: processing received
NACKs received over a time window to make a slow MCS adaptation
decision.
12. A mobile device comprising: a wireless access radio configured
to receive packets; a fast link adaptation information generator
configured to generate fast MCS (modulation and coding scheme) link
adaptation information based on incorrectly received packets, and
to transmit the fast MCS link adaptation information using the
wireless access radio, by transmitting NACKs (negative
acknowledgements) that indicate which packets were received
incorrectly and transmitting fast MCS link adaptation information
in association with the NACKs when the NACKs transmitted by the
mobile device satisfy at least one other criteria; wherein
transmitting fast MCS link adaptation information when the NACKs
transmitted by the mobile device satisfy at least one other
criteria comprises: transmitting fast MCS link adaptation
information when the transmitted NACKs include a number of
transmitted NACKs within a sliding window that is greater than a
predefined number.
13. A wireless network comprising: a transmitter that transmits
packets; a receiver that receives fast MCS (modulation and coding
scheme) link adaptation information based on transmitted packets
that were incorrectly received by receiving NACKs (negative
acknowledgements) that indicate which packets were received
incorrectly and receiving fast MCS link adaptation information in
association with the NACKs when the NACKs satisfy at least one
other criteria; a fast link adaptation information processor that
adjusts an MCS used to transmit the packets based on the fast MCS
link adaptation information; wherein receiving fast MCS link
adaptation information when the NACKs received from a mobile device
satisfy at least one other criteria comprises: receiving fast MCS
link adaptation information when the received NACKs include a
number of received NACKs within a sliding window that is greater
than a predefined number.
Description
FIELD OF THE APPLICATION
The application relates to the transmission of packets such as VoIP
(Voice over Internet Protocol) packets over a wireless link, and to
methods of adapting an MCS (modulation and coding scheme) used for
such transmission.
BACKGROUND
VoIP enables telephony over the Internet or through any other
IP-based network. Many wireless networks such as UMTS (Universal
Mobile Telecommunications System) networks currently support VoIP
service for mobile devices. 3GPP LTE (Long Term Evolution) is a
Third Generation Partnership Project that sets out to improve the
UMTS mobile phone standard in order to cope with future
requirements. So far 3GPP LTE assumes that fast link adaptation
should be supported for VoIP. Fast link adaptation involves
matching modulation, coding, and protocol parameters in accordance
with conditions of the radio link.
In order to match the modulation and coding scheme, fast link
adaptation involves quick channel state feedback to the
transmitter. Unfortunately, this can introduce a substantial
overhead, for example as high as 5 information bits/2 ms/user for
full fast link adaptation during an HSDPA (High-Speed Downlink
Packet Access) operation. The number of VoIP users can be very
large. For example, it has been shown that about 300 voice users
can be supported in 5 MHz, 12.2 KBPS AMR (Adaptive Multi-Rate) and
5% outage (see TR 25.814, Physical Layer Aspects for EUTRAN
(evolved universal terrestrial radio access network)). If each VoIP
user uses fast link adaptation, then the total overhead could be
significant, especially on the uplink. This can reduce system
capacity as well as increase link interference. Fast link
adaptation using uplink signalling can also increase power
consumption for mobile devices causing shorter battery life.
It has been shown that for low constant rate services like VoIP,
most of the AMC (adaptive modulation and coding) gain comes from
HARQ (Hybrid Automatic Repeat-reQuest) rather than from fast link
adaptation. This is partially due to the fact that the variation of
voice payload size is not large compared to that of background
data. The effectiveness of fast link adaptation can be reduced for
traffic featuring this low variation of payload size. For the most
part, the HARQ process compensates for the fast-fading effect
effectively.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments will now be described with reference to the attached
drawings in which:
FIGS. 1A to 1D are signalling diagrams showing slow link
adaptation;
FIGS. 2 to 5 are flowcharts of methods of performing MCS
adaptation;
FIGS. 6 and 7 are block diagrams of a wireless system; and
FIG. 8 is a block diagram of a mobile device.
DETAILED DESCRIPTION OF EMBODIMENTS
According to one broad aspect, the application provides a method in
a mobile device comprising: receiving packets; transmitting fast
MCS link adaptation information based on incorrectly received
packets.
According to another broad aspect, the application provides a
method in a wireless network comprising: transmitting packets;
receiving at the wireless network fast MCS link adaptation
information based on transmitted packets that were incorrectly
received; based on the fast MCS link adaptation information,
adjusting an MCS used to transmit the packets.
According to another broad aspect, the application provides a
mobile device comprising: a wireless access radio configured to
receive packets; a fast link adaptation information generator
configured to generate fast MCS link adaptation information based
on incorrectly received packets, and to transmit the fast MCS link
adaptation information using the wireless access radio.
According to another broad aspect, the application provides a
wireless network comprising: a transmitter that transmits packets;
a receiver that receives fast MCS link adaptation information based
on transmitted packets that were incorrectly received; a fast link
adaptation information processor that adjusts an MCS used to
transmit the packets based on the fast MCS link adaptation
information.
Further embodiments provide computer readable media having computer
executable instructions stored thereon, for execution by a wireless
device or network device for example, that control the execution of
one or more of the methods summarized above, or described
below.
Methods of Slow Link Adaptation
Methods of performing slow link adaptation are described in
applicants co-pending U.S. application Ser. No. 11/690,615 filed
Mar. 23, 2007 entitled "Slow Adaptive Modulation and Coding State
(MCS) for LTE VoIP", hereby incorporated by reference in its
entirety. Some of the methods are based on NACK-only (negative
acknowledgement-only) feedback with no explicit signaling of the
MCS. Other of the methods are based on explicit signaling by the
mobile device to the network indicating a requested MCS. This can
be an absolute or relative (to current MCS) decision. More
generally, the feedback mechanism can be based on layer 1 CQI
signalling or layer 2 signalling.
A specific example of performing slow link adaptation based on NACK
feedback rate will now be described. The mobile device is already
feeding back NACK information, and this is then used to derive a
suitable MCS for the user. In a specific example, the network
monitors the mobile device's NACK rate and, based on the NACK rate,
slowly makes changes to the mobile device's assigned MCS. In some
cases, NACK-only feedback is employed, in which case the mobile
device transmits NACKs, but does not transmit ACKs. The detailed
embodiments apply to received packets that are VoIP packets. More
generally, embodiments may find application to receiving constant
rate packets, receiving real-time packets, or receiving constant
rate real-time packets.
For example, consider a mobile device that is initially assigned
M=16 QAM, C=3/4 (where 1/C represents the amount of coding
redundancy, and hence, the coding's robustness, and M represents
the modulation scheme). If, after a period of time, the network
detects a NACK feedback rate which is larger than the transition
threshold, the network switches the mobile device to more
conservative modulation and coding requirements (for example, with
M=QPSK, C=1/2). An advantage is that there is no need for channel
feedback from the mobile device so both the mobile device's battery
consumption and uplink interference can be reduced. The
disadvantage is that the reaction time to adjust the MCS may be
longer than direct feedback. A specific example using NACK/ACK
feedback is shown in FIG. 1A. In this example, a sequence of
received NACKs/ACKs is indicated at 402. where the solid lines
(such as line 404) represent NACKs, and the hollow lines (such as
line 406) represent ACKs. The number of NACKs received over a
sliding window 400 is monitored, and if the NACK rate is high, then
the mobile device is moved to a more conservative MCS.
In a specific example of using explicit signalling to transmit an
MCS request from the mobile device, layer 1 signalling for slow
link adaptation comprising a 1 bit CQI can be utilized for
signaling the request, the 1 bit indicating a relative decision on
the MCS compared to the previous MCS. An example of this is shown
in FIG. 1B which is a signalling diagram showing Layer 1 signalling
for slow link adaptation. In the illustrated example, CQI feedback
414 is sent for example every T=100 ms In a specific example, a 5
bit CQI feedback is employed, and a repetition code is used to
repeat the single bit 5 times to improve the reliability.
In another example, mobile devices may feed back an absolute
average channel quantity to the base station. This might for
example be a 5 Bit CQI information field that is fed back in a very
slow rate, e.g., to "fit" for the user equipment's (UE's) average
SNR condition. The base station makes slow link adaptation
decisions based on this feedback.
In another specific example of using explicit signalling, layer 2
signalling consisting of MAC layer signalling is employed. This
may, for example, performed with an optional MAC header of the MAC
PDU (medium access control payload data unit) transmitted from the
mobile device to the base station. Alternatively, it could be
separate MAC control signaling. FIG. 1C is a signalling diagram
showing in-band MAC layer signalling for slow link adaptation. By
using MAC signaling, the layer 1 CQI can be turned off completely.
In the specific example shown in FIG. 1C, an uplink voice packet is
indicated at 410 and in-band MAC layer signalling is indicated at
412. The MAC signaling may be repeated multiple times to further
enhance the reliability as shown in FIG. 1D which shows a
signalling diagram featuring quick repeat of MAC layer signalling.
In the specific example shown in FIG. 1D, uplink voice packets are
indicated at 4120,422,424 and in-band MAC layer signalling 426 is
repeated three times.
Further methods of performing slow link adaptation are described in
applicants co-pending U.S. application Ser. No. 11/741,571 filed
Apr. 27, 2007 hereby incorporated by reference in its entirety.
Some of the methods are based on ACK-only feedback with no explicit
signaling of the MCS. These are similar to the above-described
methods based on NACK-only feedback, but using ACK-only feedback
instead.
Fast MCS Adaptation
All the embodiments described above have involved slow MCS
adaptation. The MCS is updated on the basis of information that is
accumulated over some period of time, be it a number of ACKs or
NACKs over a time, an average SNR over a time period etc. In
another embodiment, methods and systems for performing fast MCS
adaptation are provided. When a mobile device receives a VoIP
packet in error, a NACK will be fed back to the base station. In
general, this may imply that the channel condition is poor. When
the channel condition is poor, it is advantageous to take measures
to improve the reliability of transmission as soon as possible, for
example by changing the MCS, to increase the likelihood of
subsequent successful transmission and reception. In some
embodiments, fast MCS link adaptation information is transmitted in
association with NACK feedback to allow the transmitter to make
quicker MCS adaptation decisions. In some embodiments, the NACK and
the fast MCS link adaptation information are combined in a code
division multiplex (CDM) manner. One example would be a scheme that
incorporates cylic shifts of a Zadoff-Chu sequence.
The NACK and fast MCS link adaptation can be combined as described
above in the context of NACK-only feedback (described previously)
or in ACK/NACK feedback.
In some embodiments, an ACK-only feedback scheme is employed, and
in such a case there are no NACKs with which to combine the fast
MCS link adaptation information.
In some embodiments, the fast MCS link adaptation information is
sent back for every VoIP packet that is received in error, but
using a mechanism other than a combination with a NACK.
In the detailed examples of fast link adaptation described below,
the fast MCS link adaptation information is a CQI (channel quality
indicator) that is fed back from the mobile device to the base
station, this consisting of information that is directly reflective
of the quality of the channel. This typically is an instantaneous
SNR (signal-to-noise ratio) or some representation of SNR. A
transmitter can look at the SNR value fed back, and make an MCS
adaptation decision based on that. More generally, the fast MCS
link adaptation information is any information that can be fed back
from the mobile device to the base station that allows a fast MCS
adaptation decision to be made at the transmitter. In some
embodiments, the link adaptation information is a received signal
value such as an SNR, RSSI (received signal strength indicator) or
RSRP (reference symbol received power). A fast MCS adaptation
decision is fast in the sense that it can be made very quickly on
the basis substantially instantaneous channel conditions reflected
by the information provided as opposed to slow adaptation
information that is a function of conditions that occur over a
period of time and/or accumulated over a period of time before a
decision is made. CQI that is fed back based on instantaneous
conditions is a specific example of fast link adaptation
information. In another example, the fast MCS link adaptation
information is more directly representative of an MCS to use. For
example, it can be an indication of the MCS that the mobile device
has determined to be appropriate based on instantaneous channel
conditions. The mobile device can determine which MCS is
appropriate in any suitable manner. In a specific example, the
mobile device measures the SNR and makes an MCS decision based on
that. The MCS decision can be fed back as a direct encoding of the
MCS. Alternatively, a differential encoding of the MCS can be
employed for the purpose of feeding back the MCS decision to the
network. For example, if changes in MCS are limited to be one or
two steps at a time, a few bits can be used to signal the change in
MCS.
In some embodiments, the fast MCS link adaptation information is
consistent with that defined for HSDPA operation with the exception
of the fact that it is not sent as frequently. This provides a
mechanism for transmitting 5 bits of CQI information every 2
ms.
In some embodiments, the fast MCS adaptation information is
consistent with that defined in LTE TR.25.814.
FIRST EXAMPLE
Feedback CQI for Every NACK
In a first specific example of fast MCS adaptation, each time a
NACK is fed back from a mobile device to the network, a CQI
(channel quality indication) is also fed back. On the basis of
this, the transmitter makes an MCS adaptation decision for the
mobile device. This decision can be to leave the MCS unchanged, or
to change the MCS.
Flowcharts of this approach are shown in FIGS. 2 and 3. FIG. 2
shows method steps executed by a mobile device, while FIG. 3 shows
method steps executed by the network.
Referring first to FIG. 2, for the mobile device, the method starts
at step 2-1 with the mobile device receiving VoIP packets. At step
2-2, the mobile device transmits NACKs that include a NACK for each
VoIP packet that was not correctly received. In step 2-3 the mobile
device also transmits fast MCS link adaptation information each
time a NACK is transmitted. A precursor to step 2-3 involves making
a determination of the fast MCS link adaptation information that is
to be fed back. Many examples have been given previously of what
this may involve.
Referring now to FIG. 3, for the network, the method starts at step
3-1 with the wireless network transmitting VoIP packets. In step
3-2, the wireless network receives NACKs (negative
acknowledgements) that include a NACK for each VoIP packet that was
not correctly received. In step 3-3, the wireless network receives
fast MCS link adaptation for each of the NACKs transmitted by the
mobile device. In step 3-4, based on the fast MCS link adaptation
information, the wireless network adjusts an MCS used to transmit
VoIP packets.
SECOND EXAMPLE
Feedback CQI Based on Number of NACKs within a Sliding Window
In a second specific example, link adaptation information such as a
CQI is fed back in association with the NACK feedback, but this
does not involve transmitting a CQI for each and every NACK. Some
additional condition needs to be satisfied before the CQI is fed
back. For example, in one implementation, the mobile device
monitors NACK transmissions (equivalently, the mobile device
monitors the number of packet received in error) for the occurrence
of a certain number of NACKs within a period defined by a sliding
window. Upon determining that the certain number of NACKs has
occurred within the period, the mobile device feeds back a CQI.
After feeding back a CQI in this manner, in some implementations,
the mobile device does not send another CQI until the next time the
condition (number of NACKs in sliding window greater than certain
number) is true. Of course, since the window is sliding, this could
be as soon as the next NACK.
Alternatively, after feeding back a CQI in this manner, the mobile
device feeds back a CQI for every NACK for some time.
As in the first example, on the basis of the CQI fed back, the
transmitter makes an MCS adaptation decision for the mobile device.
This decision can be to leave the MCS unchanged, or to change the
MCS.
Flowcharts of this approach are shown in FIGS. 4 and 5. FIG. 4
shows method steps executed by a mobile device, while FIG. 5 shows
method steps executed by the network.
Referring now to FIG. 4, for the mobile device, the method starts
at step 4-1 with the mobile device receiving VoIP packets. At step
4-2, the mobile device transmits NACKs that include a NACK for each
VoIP packet that was not correctly received. In step 4-3 the mobile
device also transmits fast MCS link adaptation information when the
NACKs transmitted by the mobile device satisfy at least one other
criteria. A specific example of such a criteria is that some number
of NACKs must have been transmitted within a sliding window.
Referring now to FIG. 5, for the network, the method starts at step
5-1 with the wireless network transmitting VoIP packets. In step
5-2, the wireless network receives NACKs that include a NACK for
each VoIP packet that was not correctly received. In step 5-3, the
wireless network receives fast MCS link adaptation when NACKs
transmitted by the mobile device satisfy at least one other
criteria. In step 5-4, based on the fast MCS link adaptation
information, the wireless network adjusts an MCS used to transmit
VoIP packets.
Fast MCS Link Adaptation in Combination with Slow MCS
Adaptation
Various methods of fast MCS link adaptation and various methods of
slow MCS link adaptation have been described. In another
embodiment, a link adaptation method is provided that features a
fast MCS adaptation method in combination with a slow MCS
adaptation method. Particular implementations might feature a
combination of one or more of the fast MCS adaptation methods
described herein combined with one or more of the slow MCS
adaptation methods described herein. In a specific example, a slow
MCS adaptation method is used as a default MCS adaptation method
and when a packet is in error, fast MCS adaptation is applied (CQI
information for example by instantly feeding back together with a
NACK).
Referring now to FIG. 6, shown is a block diagram of an example
communication system 40-1. The communication system 40-1 has a
wireless network 20-1, a mobile device 10-1 and other mobile
devices 30-1; the communication system 40-1 may have other
components, but they are not shown for sake of simplicity. For
example, the mobile device and the network will each have
transmitters and receivers, and one or more antennas each. The
mobile device 10-1 has a wireless access radio 16-1, a processor
17-1, and a fast link adaptation information generator (based on
incorrectly received packets) 15. The mobile device 10-1 may have
other components, but they are not shown for sake of simplicity.
The other mobile devices 30-1 may each have components similar to
those of the mobile device 10-1. Alternatively, some or all of the
other mobile devices 30-1 may have different components than those
of the mobile device 10-1. The wireless network 20-1 has a fast
link adaptation information (based on incorrectly received packets)
processor 22. The wireless network 40-1 also has a transmitter 25
and a receiver 27. In some embodiments, the fast link adaptation
information processor 22, the transmitter 25, and the receiver 27
all form part of a base station or other network element that
provides wireless access.
In operation, the mobile device 10-1 communicates with the wireless
network 20-1 using its wireless access radio 16-1. The wireless
communication is over a wireless connection 19-1 between the mobile
device 10-1 and the wireless network 20-1. The other mobile devices
30-1 may similarly communicate with the wireless network 20-1 over
respective wireless connections (not shown). The communication with
the wireless network 20-1 might for example be telephony, or other
forms of communication such as email. The fast link adaptation
information generator 15 generates fast link adaptation information
based on incorrectly received packets by the mobile device 10-1.
Various detailed examples are given above. In the wireless network
20-1, the fast link adaptation information processor 22 processes
the feedback, and performs link adaptation accordingly. In some
embodiments, the fast MCS link adaptation can be sent in
association with NACKs as described previously, for example once
for every NACK, or based on NACKs received within a sliding window.
However, in the absence of NACK feedback another mechanism is used,
as described previously.
In the illustrated example, the fast link adaptation information
generator 15 is implemented as software and is executed on the
processor 17-1. However, more generally, the fast-link adaptation
information generator 15 may be implemented as software, hardware,
firmware, or any appropriate combination thereof. Similarly, the
fast link adaptation processor 22 may be implemented as software,
hardware, firmware, or any appropriate combination thereof.
Referring now to FIG. 7, shown is a block diagram of an example
communication system 40-2 for implementing mobile device assisted
MCS adaptation. The communication system 40-2 has a wireless
network 20-2, a mobile device 10-2, and other mobile devices 30-2;
the communication system 40-2 may have other components, but they
are not shown for sake of simplicity. The mobile device 10-2 has a
wireless access radio 16-2, a processor 17-2, a slow link
adaptation information generator 18 and a fast link adaptation
information generator 21. The mobile device 10-2 may have other
components, but they are not shown for sake of simplicity. The
other mobile devices 30-2 may each have components similar to those
of the mobile device 10-2. Alternatively, some or all of the other
mobile devices 30-2 may have different components than those of the
mobile device 10-2. The wireless network 20-2 has a slow link
adaptation information and fast link adaptation information
processor 24 that performs MCS adaptation based on the slow link
adaptation information and the fast link adaptation information
received from the mobile device. The wireless network also has a
transmitter 25 and a receiver 27. In some embodiments, the slow
link adaptation information and fast link adaptation information
processor 24, the transmitter 25, and the receiver 27 all form part
of a base station or other network element that provides wireless
access.
In operation, the mobile device 10-2 communicates with the wireless
network 20-2 using its wireless access radio 16-2. The wireless
communication is over a wireless connection 19-2 between the mobile
device 10-2 and the wireless network 20-2. The other mobile devices
30-2 may similarly communicate with the wireless network 20-2 over
respective wireless connections (not shown). The communication with
the wireless network 20-2 might for example be telephony, or other
forms of communication such as email. The slow link adaptation
information generator 18 generates and transmits slow link
adaptation information to network. Various examples of how this
might be done, and what this might constitute, are described above.
In addition, the fast link adaptation information generator 21
generates and transmits fast link adaptation information to the
network. Again, various examples of how this might be done, and
what this might constitute, are described above. The slow link
adaptation information and fast link adaptation information
processor takes both types of link adaptation information and
performs MCS adaptation based thereon. This can be done in a joint
fashion (considering both types of feedback when both are
available) or more or less independently (considering each type of
feedback on its own as it is received).
Another Mobile Device
Referring now to FIG. 8, shown is a block diagram of another mobile
device that may implement any of the mobile device methods
described herein. The mobile device 100 is shown with specific
components for implementing features similar to those of the mobile
device 10-1 of FIG. 6 or mobile device 10-2 of FIG. 7. It is to be
understood that the mobile device 100 is shown with very specific
details for example purposes only.
A processing device (a microprocessor 128) is shown schematically
as coupled between a keyboard 114 and a display 126. The
microprocessor 128 is a type of processor with features similar to
those of the processor 14 of the mobile devices shown in FIGS. 6
and 7. The microprocessor 128 controls operation of the display
126, as well as overall operation of the mobile device 100, in
response to actuation of keys on the keyboard 114 by a user.
The mobile device 100 has a housing that may be elongated
vertically, or may take on other sizes and shapes (including
clamshell housing structures). The keyboard 114 may include a mode
selection key, or other hardware or software for switching between
text entry and telephony entry.
In addition to the microprocessor 128, other parts of the mobile
device 100 are shown schematically. These include: a communications
subsystem 170; a short-range communications subsystem 102; the
keyboard 114 and the display 126, along with other input/output
devices including a set of LEDS 104, a set of auxiliary I/O devices
106, a serial port 108, a speaker 111 and a microphone 112; as well
as memory devices including a flash memory 116 and a Random Access
Memory (RAM) 118; and various other device subsystems 120. The
mobile device 100 may have a battery 121 to power the active
elements of the mobile device 100. The mobile device 100 is in some
embodiments a two-way radio frequency (RF) communication device
having voice and data communication capabilities. In addition, the
mobile device 100 in some embodiments has the capability to
communicate with other computer systems via the Internet.
Operating system software executed by the microprocessor 128 is in
some embodiments stored in a persistent store, such as the flash
memory 116, but may be stored in other types of memory devices,
such as a read only memory (ROM) or similar storage element. In
addition, system software, specific device applications, or parts
thereof, may be temporarily loaded into a volatile store, such as
the RAM 118. Communication signals received by the mobile device
100 may also be stored to the RAM 118.
The microprocessor 128, in addition to its operating system
functions, enables execution of software applications on the mobile
device 100. A predetermined set of software applications that
control basic device operations, such as a voice communications
module 130A and a data communications module 130B, may be installed
on the mobile device 100 during manufacture. In addition, a
personal information manager (PIM) application module 130C may also
be installed on the mobile device 100 during manufacture. The PIM
application is in some embodiments capable of organizing and
managing data items, such as e-mail, calendar events, voice mails,
appointments, and task items. The PIM application is also in some
embodiments capable of sending and receiving data items via a
wireless network 110. In some embodiments, the data items managed
by the PIM application are seamlessly integrated, synchronized and
updated via the wireless network 110 with the device user's
corresponding data items stored or associated with a host computer
system. As well, additional software modules, illustrated as
another software module 130N, may be installed during manufacture.
One or more of the modules 130A,130B,130C,130N of the flash memory
116 can be configured for implementing features similar to those of
the mobile device shown in FIGS. 6 and 7.
Communication functions, including data and voice communications,
are performed through the communication subsystem 170, and possibly
through the short-range communications subsystem 102. The
communication subsystem 170 includes a receiver 150, a transmitter
152 and one or more antennas, illustrated as a receive antenna 154
and a transmit antenna 156. In addition, the communication
subsystem 170 also includes a processing module, such as a digital
signal processor (DSP) 158, and local oscillators (LOs) 160. The
communication subsystem 170 having the transmitter 152 and the
receiver 150 is an implementation of a wireless access radio with
features similar to those of the wireless access radio of the
mobile device 10 shown in FIGS. 6 and 7. The specific design and
implementation of the communication subsystem 170 is dependent upon
the communication network in which the mobile device 100 is
intended to operate. For example, the communication subsystem 170
of the mobile device 100 may be designed to operate with the
Mobitex.TM., DataTAC.TM. or General Packet Radio Service (GPRS)
mobile data communication networks and also designed to operate
with any of a variety of voice communication networks, such as
Advanced Mobile Phone Service (AMPS), Time Division Multiple Access
(TDMA), Code Division Multiple Access (CDMA), Personal
Communications Service (PCS), Global System for Mobile
Communications (GSM), etc. The communication subsystem 170 may also
be designed to operate with an 802.11 Wi-Fi network, and/or an
802.16 WiMAX network. Other types of data and voice networks, both
separate and integrated, may also be utilized with the mobile
device 100.
Network access may vary depending upon the type of communication
system. For example, in the Mobitex.TM. and DataTAC.TM. networks,
mobile devices are registered on the network using a unique
Personal Identification Number (PIN) associated with each device.
In GPRS networks, however, network access is typically associated
with a subscriber or user of a device. A GPRS device therefore
typically has a subscriber identity module, commonly referred to as
a Subscriber Identity Module (SIM) card, in order to operate on a
GPRS network.
When network registration or activation procedures have been
completed, the mobile device 100 may send and receive communication
signals over the communication network 110. Signals received from
the communication network 110 by the receive antenna 154 are routed
to the receiver 150, which provides for signal amplification,
frequency down conversion, filtering, channel selection, etc., and
may also provide analog to digital conversion. Analog-to-digital
conversion of the received signal allows the DSP 158 to perform
more complex communication functions, such as demodulation and
decoding. In a similar manner, signals to be transmitted to the
network 110 are processed (e.g., modulated and encoded) by the DSP
158 and are then provided to the transmitter 152 for digital to
analog conversion, frequency up conversion, filtering,
amplification and transmission to the communication network 110 (or
networks) via the transmit antenna 156.
In addition to processing communication signals, the DSP 158
provides for control of the receiver 150 and the transmitter 152.
For example, gains applied to communication signals in the receiver
150 and the transmitter 152 may be adaptively controlled through
automatic gain control algorithms implemented in the DSP 158.
In a data communication mode, a received signal, such as a text
message or web page download, is processed by the communication
subsystem 170 and is input to the microprocessor 128. The received
signal is then further processed by the microprocessor 128 for an
output to the display 126, or alternatively to some other auxiliary
I/O devices 106. A device user may also compose data items, such as
e-mail messages, using the keyboard 114 and/or some other auxiliary
I/O device 106, such as a touchpad, a rocker switch, a thumb-wheel,
or some other type of input device. The composed data items may
then be transmitted over the communication network 110 via the
communication subsystem 170.
In a voice communication mode, overall operation of the device is
substantially similar to the data communication mode, except that
received signals are output to a speaker 111, and signals for
transmission are generated by a microphone 112. Alternative voice
or audio I/O subsystems, such as a voice message recording
subsystem, may also be implemented on the mobile device 100. In
addition, the display 126 may also be utilized in voice
communication mode, for example, to display the identity of a
calling party, the duration of a voice call, or other voice call
related information.
The short-range communications subsystem 102 enables communication
between the mobile device 100 and other proximate systems or
devices, which need not necessarily be similar devices. For
example, the short-range communications subsystem may include an
infrared device and associated circuits and components, or a
Bluetooth.TM. communication module to provide for communication
with similarly-enabled systems and devices.
Numerous modifications and variations of the present application
are possible in light of the above teachings. It is therefore to be
understood that within the scope of the appended claims, the
application may be practised otherwise than as specifically
described herein.
* * * * *